Purifying dry-cleaning solvent



Patented Mar. 5, 1 929.

ARTHUR EDWARD HATFIELD, OF LEYTONSTONE, LONDON, ENGLANZQ, ASSIGNOR OF ONE-HALF T ACHILLE SERRE LIMITED, 01 HACKNEY WICK, ENGLAND, A BRITISH COMPANY.

No Drawing. Application filed September 30, .1926, Serial No. 138,809, and in Great Britain December 31, 1925.

This invention relates to improvements in dry cleaning, by which term I include wool scouring by means of solvents, and hasfor its object to provide an improved process for 5 clarifying and dehydrating the soiled solvent in the washing machines.

Hitherto the solvent used for this purpose has been clarified and dehydrated by various v means such as processes of filtration, the use of centrifugal separators, or dissociation, or precipitation by various chemical reagents. Tests have shown, however, that in no cases is the effluent perfectly free'of moisture and foreign matter. For example, experiments 1 carried out with centrifugal separators have shown that not all of the suspended impurities and moisture are removed but that a gelatinous residue remains formed by the moisture in the goods being cleaned emulsifying with a percentage of the soaps and oils liberated and in-many cases with the soap used in dry cleaning. This residue holds finely divided solid matter in the collodial state and it is impossible to remove it by mechanical means.

It hasbeen proposed in a process of removing oily ink from material containing the same by means of a solvent, such as benzine, to pass the soiled .solvent into a tank in which it is treated with a substance such I asclay, infusorial earth, carbon, and" the like. The solvent is then passed to a filter press and the filtrate is run into a still'where it is evaporated, the heavy oil in the solvent being recovered while the solvent itself is condensed and assed to a storage tank.

I have now ound that if, in the process 1 of dry cleaning, the soiled solvent is treated withafinely divided porous cellular sil'ca (hereinafter referred to asfilter aid) 0 a sufficiently low specific gravity and the solvent containingfthe particles of the said filter aid in suspension is passed to a filter,

the filtrate is'substantially free of moisture and foreign matter and can be passed back to the washing machine in a. continuous cyclic process.

Further, the rate at which the solvent is passed through-the washing machine can be increased to such an extent that'once in every five minutes or less the bath is changed, by which I mean, a volume ofsolvent equal to the volume of the bath is run into and removed from the washing machine while the Working level of the solvent in the washing machine is always maintained. It is essential, that the filter aid in addition to being of low specific gravity, should be sufiiciently porous to maintain the emulsions and suspended dirt in a porous state when held against the filter. The specific avity of the filter aid should not be su stantlally more that about 12 pounds per cubic foot- (that is to say not more than 3 or 4 pounds in excess of 12 pounds per cubic foot), calculated on the wet process, i. e., from the volume occupied by the material after mixing it with water and allowin it to stand for 12 hours, or alternatively w en the filter aid is gently sifted through air into a box of known capacity and the excess scraped 0 without tamping. Distillation, or other equivalent processes are not required until the solvent becomes ovetrladen with oils, soaps and other fatty matters in solution. The process may be carried out in the following manner. 7 v

The soiled articles of clothing, or the like, to be dry cleaned are placed in a washin machine to which is added the solvent an soap necessary; for the cleaning of such, goods. The machine is set in motion by any ordinary means and the soiled'solvent is withdrawn from the washing machine and delivered to an agitating tank in which suit-. able filter aid in accordance'with this invention is placed. As hereinbe fore mentioned a preferred type of filter aid is described in British Patents Nos. 229,021 and 234,735. This is agitated with the dirty solvent which is then pumped to a filter press where the filter aid together. with the dirtand emulsions are retained. Such filter aid as has beenmentioned has also the roperty of absorbing moisture from the cleaning solvents and dehydrating the same. I It may be used in conjunction or admixed with finely divided decolorizing carbons or vegetable charcoals which assist in removing minute traces of colouring matters in solu-' tion. The decolorizing medium may be such- ,asto" absorb the coloring material or to cause it to flocculate. The solvent after it has been passed through the filterpress in.

machine. The washing machine, agitator or mixing vessel, pump and filter press are in continuous connection so that the dirty solvent passes out of the washing machine, is mixed with the 'filter aid, pumped to the press and returned'to the washing machine in such a manner that the washing machine during thewashing process is-kept continuously flushedwith clear solvent at such a rate that the bath in the washing machine is changed say six times within a washing cycle which will usually take from 10 to 20 minutes. In order to assist in maintaining a porous mass in the filter press the salts or hydroxides of the alkaline metals including such reagents as caustic potash, caustic soda or ammgn'ia, the carbonates of potash, soda .or ammonia or other'chemicals such as aluminate' of soda, or silicate of soda may be' continuously agitated or mixed with the solvent before or after the addition of the filter aid and are subsequently neutralized byinorganic acids such as sulphuric acid. Alternatively the dirty solvent (before or after the addition of the filter aid) may be treated with sulphonated oils such as those referred to in British patent specification N 0. 176,540. These reagents have the action ofsuspending materials and causing the immediate flocculation of the foreign bodies contained in the solvent, and maintaining them in a more porous state. Instead of the use of an agitating tank the filter aid may be run or pumped continuously during the process into a pipe line along which the solvent passes from the washing machine to the filter press and such pipe line may be suitably designed to assist in the thorough mixingpf the filter aid and any reagents that may e employed with the solvent.

The solvent on re-entering the washing machine is' then substantially free of all impurities and is in a somewhat similar condition to that when entering the machine at the commencement ofthe operation, except that soluble matters which" are added or extracted from the. goods during the cleaning operation remain in solution. The solution of solvent'and s'oap may be used repeatedly for subsequent operations until 7 such time as there is a surcharge ofsoluble matters when distillation. or equivalent treatment becomes necessary. The fatty acids 01? the solvent soaps can be recovered and refined and used over other purposes. 7 I

The filter press used in accordance with this invention should be fed by a-pump, or

again or employed for pumps, in such manner that a constant rate of fiow is maintained through the washing machine, or where a number of washin machines areused, arran ements should be made to secure a substantially constant flow through each washing machine. The filter should be so proportioned that the pressure does not rise toan extent necessitating cleanblown or washed down and removed from the main press, and mixed up and fed to another press for final drying, in order to allow the main press to work with a minimum of lost time. In such cases, self discharging presses may be used for the main press, but in general any known-type of pressure filter may be employed.

It will be seen that according to this invention, at the end of the operation, the soiled solvent soap solution removed from the washing machine is completely dehydrated and all colloidal suspensions removed. The time for the operation may vary from 10 to 30 minutes, according to the amount and quality of the filter aid and the reagents used and the capacity of the filter-press employed. Further, each cleaning operation is conducted in a shorter time and since the same solvent and soapsolution can be used over again for a much larger number of times there is efiected a great economy of both solvent and soap. I

' What I claim is 1. A process for clarifying and dehydrating the soiled solvent of washing machines used for dry cleaning, consisting in withdrawing the soiledsolyent from the washin machine adding to the soiled solvent fine y divided porous cellular silica of low specific gravity, passing the solvent containing articles of said silica in suspension to a filtered-solvent to the washing machine in a continuous. cyclic process. i 2. A process for clarifying anddehydratter, therefiltering the solvent, and then returning the ing the soiled'solvent of washing machines iisedflfor' dry. cleaning, consisting in withdrawing the soiledfsolvent from the washing machine, adding' tofthesoiled solvent finely divided porous cellular silica of low specific,

machine, adding to the soiled solvent finely divided porous cellularsilica. of low specific I gravity, also adding to the soiled solvent a reagent adapted to cause immediate flocculation of the foreign bodies contained in the solvent; passing the solvent containing particles of said silica in suspension to a filter, there filtering the solvent, and then returning the filtered solvent to the washing machine in a continuous cyclic process.

4. A process for clarifying and dehydrating the soiled solvent of washing'machines used for dry cleaning, consisting in withdrawing the soiled solvent from the washing machine, adding to the soiled solvent finely divided porous cellular silica of low specific gravity and a decolorizing medium, passing the solvent'containing particles of said silica in suspension to a filter, there filtering the solvent, and then returning the filtered solvent to the washing machine in a continuous cyclic process.

5. A process for clarifying and dehydrating the soiled solvent of washing machines used for dry cleaning, consisting in withdrawing the soiled solvent from the Washing machine, adding to the soiled solvent finelv divided porous cellular silica of low speci c gravity and decolorizing carbon, passing the solvent containing particles of said silica in suspension to a filter, there filtering the solvent, and then returning the filtered solvent to the washing machine in a continuous cyclic process.

6. A process for clarifying and dehydrating the soiled solvent of washing machines used for dry cleaning, consisting in withdrawing the soiled solvent from the washing machine, adding to the soiled solvent finely divided porous cellular silica of low specific gravity and decolorizing carbon, also addmg to the soiled solvent a reagent adapted to cause immediate flocculation of the foreign bodies contained in the solvent, passing the solvent containing particles'of said siliea in suspension to a filter, there filtering the solvent, and then returningthe filtered solvent to the Washing machine in a continuous cyclic process.

7. A process for clarifying and dehydrating the soiled solvent of washing machines used for dry cleaning, consisting in with drawing the soiled solvent from the washing machine, passing the soiled solvent to a filterfthere filtering the solvent, returning the filtered solvent to the Washing machine in a continuous cyclic process, and during the process adding finely divided porous cellular silica to the soiled solvent.

In testimony whereof I have signed my name to this specification.

' ARTHUR EDWARD HATFIELD.

CERTIFICATE OF CORRECTION.

Patent No. l, 704, 604.

Granted MarchQS, 1929. to

ARTHUR EDWARD HATFIELD.

It is'he'rebycertified that error appears in the printed specification. of the above numbered patent requiringcorrection as follows; Page 1. line 7 2. after @theword "tamping" insert the sentence Y'A very suitable type of filter aid for use according to this inventiom is described in British patents Nos. 229,021 and 234,735"; and'that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

(Seal) Signed and sealed this 2nd day of April, A. o. 1929.

M. J. Moore, Acting'Commission'er of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 1,704,604. Granted March 5, 1929, to

ARTHUR EDWARD HATFIELD.

it is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, fine 72, after the word "tamping" insert the sentence "A very suitable type of filter aid for use according to this invention is described in British patents Nos. 229,021 and 234,735"; and that the said Letters Patent shouid be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of April, A. D. 1929.

M. J. Moore, (Seal) Acting Commissioner of Patents. I 

